1. Field of the Invention
The present invention relates, in general, to systems and methods of dissipating heat from electronic components, and more particularly, to a heat sink assembly for use with an edge connector, such as connectors used with PC cards, printed circuit boards, and the like, that includes a plurality of fins connected to power and ground traces to conduct heat away from the edge connector contacts.
2. Relevant Background
In the computer industry, there is a continuing demand for improvements in electrical devices, such as power supplies, to enhance performance while also trying to reduce size of components. Many of these electrical devices are provided using integrated circuits or chips that are provided on printed circuit boards (PCBs). While decreasing in overall size, operating speeds, chip sizes, and numbers of transistors and other components on each printed circuit board is increasing. This leads to increased power consumption, with many chips consuming 30 watts or more of power, which in turn significantly increases the amount of heat generated by the components. Excessive heat can reduce capacity of the components and also reduce component life and reliability. As a result, many efforts have been made to control or limit heat generated during operation of the electrical components and to dissipate generated heat to reduce operating temperatures.
More specifically, many printed circuit boards, PC cards, and other thin electrical components utilize edge connectors to allow them to be plugged into a socket of another circuit board to exchange electrical signals, such as power and data signals. Typically, edge connectors generally include connectors on the edge of boards or cards made of strips of copper, gold, or other conductive metals that provide the signal, power, and ground contacts. All connectors, though, are limited in the amount of current that can be safely and effectively carried. Current flowing through the contact resistance generates heat and this raises the temperature of the contact. The temperature of each contact must be controlled to establish operating temperatures that allow reliable operation of the contact and to avoid heat damage to adjacent components.
Edge connectors in particular are designed to pass low level logic signals and not necessarily to pass higher levels of current. The current rating of edge connector contacts is typically further reduced as the ambient temperature near the connector increases. The ambient temperature is a concern in many existing edge connector designs that use a large number of parallel contacts to carry higher currents, such as in a power supply. The heat dissipating, by radiation and convection, from the contacts creates localized heating that further reduces the current that can be drawn through the edge connector.
In an attempt to control temperatures of power and ground contacts, printed circuit boards have been manufactured with continuous wiring board etches or traces between adjacent contacts. This increases the amount of surface area available to dissipate generated heat but has not been effective in meeting the continually increasing demands for higher current capacity for connectors. The demand for reduced sizes of electronic components, including edge connectors, increases the difficulty of providing additional surface area for heat transfer. For example, structural integrity is a challenge facing electronic, component manufacturers as most components are manufactured from electrically conductive material with lower mechanical strengths and with very small dimensions, e.g., a few millimeters or less in thickness. Vibration and shock can rapidly damage heat dissipation assemblies, such as metal fins, that are attached to printed circuit boards, and such assemblies are often difficult to install without damage, e.g., bending that crimps fins which reduces surface areas and can cause electrical shorting of adjacent components. Alternatively, increasing the number of contacts can sometimes be used to control individual contact temperatures but typically is not a viable option as the number of contact pairs in a connector is usually fixed.
Hence, there remains a need for an improved method and apparatus for dissipating heat from edge connectors. Preferably, such a method and apparatus would be relatively inexpensive to manufacture, would be structurally reliable, and would increase the current rating and reliability of the edge connector.
The present invention addresses the above discussed and additional problems by providing a heat sink assembly for use with typical edge connectors, e.g., card edge connectors, of cards or printed circuit boards. The heat sink assembly is adapted to provide a relatively large heat transfer capacity to control temperatures in contacts. In effect, this increases the current rating of the connector by allowing more current to pass through the connector while remaining below a preset maximum temperature. Significantly, the heat sink assembly includes a plurality of fins that are attached to the edge connector leads, such as the power and ground leads, through direct thermal connection to traces in the board. In a preferred embodiment, the fins are connected to the power and ground configuration in an alternating or interweaved fashion, such as with a pair of power leads being connected to a first fin and a pair of ground leads being connected to a second fin and so on across the edge connector. The fins are fabricated from thermal conducting material, such as copper, and heat is conducted to the fins where it is removed by convection and/or radiation due to the relatively large surface area of the fins. Since current is also conducted to the fins, adjacent fins are electrically isolated within the heat sink assembly such that power and ground fins do not come in contact.
More particularly, a printed circuit board with enhanced heat dissipation, and therefore, higher current rating is provided that includes a board with an edge connector. The edge connector is made up of a plurality of power leads and ground leads. Traces or conductor lines are provided in the board and are connected to the leads to pass current between the leads and other devices on the board. A heat sink assembly is mounted on the board to dissipate the heat generated by the leads and is thermally connected to the traces to create a heat transfer path away from the power and ground leads. In one embodiment, the power leads are positioned in one layer or surface of the board and the ground leads are positioned in a second layer or surface of the board. Slots are provided in the board for receiving contacts of the heat sink assembly, which allows connection to traces in either of the two layers. In a preferred embodiment, the heat sink assembly includes a plurality of fins and the fins are alternatively connected to power and ground leads. The heat sink assembly includes fin holders with base members having slots for receiving tips of the fins and isolation members between the slots for electrically isolating adjacent fins which are oppositely charged by the traces.